1. Field of the Invention
The present invention generally relates to power, and particularly to a power source module.
2. Description of Related Art
Power source modules are used to receive alternating current (AC) power from an AC power supply, and generate direct current (DC) power to power up electronic products. Referring to FIG. 6, a conventional power source module 100 connects an AC power supply 888 with a load 999. The power source module 100 includes an input processing circuit 102, a power switch 104, a converter 106, an output processing circuit 108, a comparator 110, a PWM (Pulse Width Modulation) control circuit 112, and a reference voltage circuit 114.
The input processing circuit 102 receives a first AC voltage from the AC power supply 888 and rectifies and filters the first AC voltage to obtain a first DC voltage. The first DC voltage is converted to a pulse voltage by the power switch 104. The pulse voltage is converted to a second AC voltage by the converter 106. The second AC voltage is rectified and filtered by the output processing circuit 108. The output processing circuit 108 generates a second DC voltage. The second DC voltage is sent to the load 999 and is fed back to the comparator 110. A reference voltage is sent to the comparator 110 from the reference voltage circuit 114. The second DC voltage is compared with the reference voltage by the comparator 110. A control signal is generated by the comparator, and is received by the PWM control circuit 112. The PWM control circuit 112 modulates an “on” duration of the power switch 104 based on the control signal to indirectly adjust the second DC power.
However, in practice, these components such as the power switch 104, the converter 106, the output processing circuit 108, and the comparator 110 are assembled on a printed circuit board (PCB) very closely to each other. Electro magnetic interference (EMI) occurs among these components. The EMI causes the second DC voltage, sent to the load 999, to be unstable. As a result, the load 999 cannot work normally and its lifetime will be shortened. Take a liquid crystal display as an example, when an unstable DC voltage is sent to the liquid crystal display, a distorted picture may be displayed.
Therefore, a power source module is needed in the industry to address the aforementioned deficiencies and inadequacies.